The present invention relates to a fiber processing agent, a glass fiber using the fiber processing agent, and a rubber product, and more specifically to a fiber processing agent that will increase the surface strength of a rubber product such as a rubber belt or a tire, a glass fiber using the fiber processing agent, and a rubber product as above containing the glass fiber.
In recent years, reinforcing fibers such as glass fiber cords have come to be widely used as a reinforcing material for reinforcing rubber products such as rubber belts and tires; however, there is a drawback that such a rubber product is repeatedly subjected to flexural stress, and hence flexural fatigue occurs leading to a drop in performance, and as a result the reinforcing material and the rubber matrix may break away from one another, and the reinforcing fibers may wear away, leading to a drop in strength being prone to occur; moreover, this phenomenon tends to be accelerated in particular by heat and moisture.
To prevent breaking away due to such flexural fatigue and thus obtain adequate reinforcement effects, it is thus necessary to strengthen the affinity and adhesion between the reinforcing fibers and the rubber, and hence the application of various fiber processing agents onto the surfaces of the reinforcing fibers has been carried out.
Various such fiber processing agents have already been proposed; for example, Japanese Laid-open Patent Publication (Kokai) No. 1-221433 discloses a fiber processing agent in which are used together a resorcinol-formaldehyde water-soluble condensate, a vinylpyridine-butadiene-styrene terpolymer latex, a dicarboxylated butadiene-styrene copolymer latex, and a chlorosulfonated polyethylene latex.
However, these days glass fibers are used in various applications; for example, in the case of use as a reinforcing material for a timing belt of a vehicle engine or the like, heat resistance and water resistance are required. As vehicle engines and the like have been made more compact and so on in recent years, this requirement has become more and more severe; in this situation, cases have started to arise in which it is difficult to meet the required quality in terms of heat resistance and water resistance with a conventional fiber processing agent as described above.
In view of this state of affairs, it is an object of the present invention to provide a fiber processing agent that exhibits excellent heat resistance and water resistance when attached to a glass fiber, a glass fiber treated with the fiber processing agent, and a rubber product that contains the glass fiber and thus has excellent durability even under a poor environment.
The present inventor carried out assiduous studies to obtain a fiber processing agent that does not bring about a drop in quality even under a poor environment, and as a result found that by using as a fiber processing agent a dispersion-type solution having as dispersoids an epoxy resin, which is excellent in terms of strength and also has excellent heat resistance and water resistance, and a rubber latex, which is flexible, a glass fiber and a rubber product can be obtained according to which durability can be greatly increased without bringing about a drop in quality even under a poor environment.
The present invention was accomplished based on this finding: a fiber processing agent according to the present invention is characterized by comprising a dispersion-type solution having a rubber latex and an epoxy resin as dispersoids.
According to the above fiber processing agent, because the fiber processing agent comprises a dispersion-type solution having a rubber latex and an epoxy resin as dispersoids, a fiber can be obtained that has a surface having ample density and elasticity and also has excellent heat resistance and water resistance.
Moreover, from the viewpoint of securing the density possessed by the epoxy resin and resistance to flexural fatigue when the fiber processing agent is used in a rubber product, it is preferable for the content of the rubber latex to be 35 to 95 wt %, and the content of the epoxy resin to be 5 to 65 wt %.
Moreover, a glass fiber according to the present invention is characterized by having a fiber processing agent as described above attached to the glass fiber in an amount of 10 to 40 wt % in terms of solids.
Because the above glass fiber has attached thereto 10 to 40 wt % in terms of solids of a fiber processing agent as described above, it is possible to attach the fiber processing agent to the fiber surface evenly and uniformly, and a glass fiber, according to which the fiber surface has ample density and elasticity, heat resistance is not degraded, and water resistance is excellent, can be obtained reliably.
Moreover, a rubber product according to the present invention is characterized by containing a glass fiber as described above.
Because the above rubber product contains the glass fiber, the rubber product can adequately withstand use in a poor environment of high temperature and high humidity, and hence the durability of a rubber product such as a timing belt can be improved.